How Common Are Blank Lincoln Cent Planchets?

Since the US Mint completely outsources the production of cent planchettes to a third party, including upsetting, I suspect these are quality control rejects from that manufacturer, either rejected by them before submission to the Mint or rejected by the Mint.

Since they make literally billions and billions and billions of these things every year it stands to reason there are going to be plenty of extras floating around somewhere in the manufacturing process.